The present invention relates to a metal paste and a method for joining components in which this metal paste is used.
Joining components, such as LEDs or very thin silicon chips, which exhibit a high sensitivity to pressure and temperature, represents a particular challenge in the field of power electronics.
For this reason, such components that are sensitive to pressure and temperature are often joined to each other by adhesion. The adhesive technique, however, has the disadvantage that it produces contact points between the components that exhibit only inadequate heat conduction or electrical conductivity.
To solve this problem, the components to be joined are frequently sintered. The sintering technique represents a very simple method for the stable joining of components.
Conventional sintering methods, however, require either a high processing pressure or else a high processing temperature. These conditions often result in damage to the components to be joined, so that conventional sintering methods must be ruled out for many applications.
In German published patent application DE 10 2007 046 901 A1 a sintering technique is proposed, with which it is possible to build joining layers with very good electrical-conductivity and heat-conduction properties for power electronics. In this sintering method a metal paste is used containing a silver compound, which decomposes into elementary silver below 300° C. These metal pastes allow a reduction of the processing pressure to below 3 bar and a reduction of the processing temperature to below 250° C. This sintering technique represents a large leap in quality in joining components that are sensitive to pressure and temperature.
However, for many applications it would be desirable if the processing temperature could be lowered even further. A lower temperature would lead to smaller loading of the components to be joined and thus to a further increase in the quality of the components in the field of power electronics. In addition, with a further decrease of the processing temperature, considerable amounts of energy costs could also be saved.